Drawout switchgear mechanism



Oct. 23, 1956 E. A. PIFKE 2,768,254

DRAWOUT SWITCHGEAR MECHANISM Filed Sept. 14, 1953 2 Sheets-Sheet l Inventor: Edgar A. PifKe His Attorney.

Oct. 23, 1 E. A. PlFKE nmwouw SWITCHGEAR MECHANISM 2 Sheets-Sheet 2 Filed Sept. 14, 1955 e i wn nA v? b H is ttorneg.

United States v Patent DRAWOUT SWITCHGEAR MECHANISM Edgar A. Pifke, Philadelphia, Pa., assignor to General Electric Company, a corporation of New York Application September 14, 1953, Serial No. 380,062 11 Claims. (Cl. 200-50) This invention relates to metal-enclosed draw-out switchgear units and, more particularly, to improvements in mechanism for effecting insertion and draw-out of said units and to improvements in the interlock means associated with said mechanisms.

In draw-out switchgear apparatus having the usual spring-loaded disconnect contacts, it is desirable, in order to overcome the frictional forces produced by the disconnect contacts, to provide a force amplifying operating mechanism for moving the switchgear unit into and out of an enclosing cubicle. One problem in the design of such force amplifying operating mechanism is that there is only a limited space available for the normally large sized mechanism necessary to obtain the desired mechanical advantage. One approach to this problem is shown in the application of Warren J. Donaldson, Serial No. 239,706, now Patent No. 2,702,324, filed August 1, 1951, and assigned to the assignee of the present invention. In that application, a high ratio force amplification is obtained by a mechanism comprising a cam and an operating lever interrelated to said cam by a reversible pawl and ratchet mechanism which makes it possible to actuate the cam from said lever by a series of repeated short operating strokes, which require very little surrounding space. This scheme is quite effective but is rather costly in view of the reversible pawl and ratchet mechanism required.

It is, therefore, an object of this invention to provide a new and an improved force amplifying mechanism.

It is a further object of this invention to provide an improved force amplifying means which requires no pawl and ratchet mechanism and is especially adapted for use with draw-out switchgear apparatus.

It is a further object of this invention to provide for a draw-out switchgear unit a simple and inexpensive force amplifying mechanism comprising an operating lever and a cam mechanism so constructed that only a single short stroke of the operating lever is required to cause said cam mechanism to produce a wide range of effective movement of said switchgear unit.

It is a further object of this invention to provide a new and improved interlock means for insuring that a switchgear unit is always tripped open before efiective movement of said operating lever can be commenced.

The objects of this invention may be carried out in one form by the provision of a cam mechanism having a pair of appropriately configured cam means interrelated to a circuit breaker unit and its enclosing cubicle in such a manner that the cam is double-acting, or more particularly, is capable of producing relative movement between said unit and said cubicle in accordance with the configuration of both of said cam means. The cam mechanism is actuable from an operating lever which is so interlocked to the tripping means for the circuit breaker unit that whenever the operating lever has been moved into a position wherein it is capable of producing effective movement of the cam mechanism, the interlock means has acted to insure tripping of the circuit breaker unit.

The invention will be better understood by considering the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Fig. l is a side view of a removable circuit breaker unit enclosed in a metal-clad cubicle with one side of the cubicle being partially broken away to show the preferred form of double-acting cam drawout mechanism and the associated interlock mechanism.

Fig. 2 is a view similar to Fig. 1 but showing the door of the cubicle opened and the operating lever withdrawn to its operative condition preparatory to applying an upward stroke for effecting withdrawal of the circuit breaker unit. Fig. 3 is a view showing the circuit breaker unit after having been cammed back into a position in which the unit is disconnected from its disconnect contacts.

Referring now to Fig. l, the removable circuit breaker unit, indicated generally at 10, includes a framework 11 having side plate 9 associated therewith, the framework being movably supported in a cubicle 12 by means of carriage 13 having rollers 14 cooperating with suitable horizontally-extending guides fixed to the cubicle 12. The framework 11 carries a circuit breaker 15 suitably insulated therefrom. The circuit breaker 15 may be of a conventional type but is shown as being of the improved type more fully described in Patent No. 2,549,441, granted to John A. Favre. The circuit breaker 15 comprises a pair of cooperating main contacts 16, 17, the contact 16 being movable to an open position by a tripfree operating mechanism (not shown) in response to predetermined overcurrent conditions. Closing operation of the movable contact 16 is effected by a manually operable handle 18 in the manner described in the aforementioned Favre patent. in addition to the usual overcurrent responsive trip means, the circuit breaker 15 is provided with a separate manual and safety interlock trip pin 19 operatively connected to the rotatable trip shaft 20 of the circuit breaker by a crank-like lever 21, to which the trip pin 19 is suitably united, as by welding.

The enclosing cubicle 12 is provided with a vertically hinged door 22 which is positively interlocked with the movable circuit breaker contact 16 so as to prevent opening of the door 22 when the circuit breaker is in closed condition. This positive interlock between the door 22 and the movable circuit breaker contact is constituted by latching lever 23 pivotally mounted at one end on a pin 24 fixed to the side plates 9 of the circuit breaker unit. At its other end the latching lever 23 has a hook portion 25, which is adapted to cooperate with an apertured bracket 26 fixed to the door 22. When the hook portion 25 is in the solid line position of Fig. l, the hook engages the aperture 27 in the bracket and prevents opening of door 22. Conversely, when the latching lever 23 is moved so that its hook portion 25 is in the dotted line position 28 of Fig. l, the door is unlatched and is free to be opened. Operative movement of the lever 23 between the solid and dotted line positions is effected through the cam action of breaker shaft 29 which moves in accordance with the movement of movable contact 16. Shaft 29 is linked to movable contact 16 through a link 30 pivotally connected at 31 to contact 16 and is guided for transverse movement in slots 30a formed in the side plates 9 of the circuit breaker unit. A reduced portion of the shaft 29 fits into a cam slot 29a formed in lever 23 so that whenever the contact 16 is in the closed position of Fig. 1, the shaft 29 will be disposed to the right and will occupy the lower end of the slot 290 as shown in Fig. 1; and, whenever the contact 16 is moved to open position as shown in Fig. 2, the shaft 29 will be moved to the left to the position of Fig. 2. Thus, it will be apparent that transverse movement of operating shaft 29 from its right hand position to its left hand position is transmitted through slot 29a to the lever 23 in such a manner that the lever 23 is pivoted counterclockwise about pivot- 24 whereby to effect unlatching, of. the door. 22. Similarly, it will be' apparent that closing the contact 16 when the door 22 is closed will effect movement of the latching; lever 23: from the position of Fig. 2 to the solid line position: of Fig. 1, whereby thedoor22 will belatchedi closed, and unopenable,, whenever the breaker is in. its closedp'ositiont The removable circuit breaker unit it is provided with suitable disconnect contacts 40 fixed to the unit and electrically connected to themain circuit breaker contacts 16 andv 17. These disconnect contacts 4t) project. from the back of the unit and. are located so that they may; be forced-into firmcircuitv closing. engagement with stationary circuit terminal contacts 41 that. are mounted oninsulating, supports 4"). extending through the back wall of the cubicle 12. As shown, the disconnect contacts 4% are composed of a plurality of conducting fingers 43 biased toward each other. by strongcompression springs 44 so as to establish a firm conducting pressure engagement between the disconnect .contacts 40 and the terminal contacts 41. This pressure engagement inherently results in a considerable frictional resistance to movement of the circuit breaker unit to and from the connected position of Fig. l. In order to overcome this frictional resistance and to facilitate manual removal and insertion of the unit, it is desirable to provide a force amplification means for effecting movement of theunit with. respect to the enclosing cubicle 12.

in the illustrated embodiment of the invention, the desired force amplification is obtainedby the use of a cam mechanism 45 comprising a double-acting cam element 46, which is pivotally mounted about an axis 47 of a shaft 50, as will be described hereinafter. Pivotal mo tion of cam element 46 is eifected by means of a manually-operable lever 43 operatively related to the cam element 46 by link 49'pivotally supported on pivots 4% and 49b fixed to the lever 48 and cam element 46, respectively. Although only a single carnelement 46 is shown, it is to be understood that in order to produce balanced camming forces a pair of cam elements, one at each side of the circuit breaker unit 10 is used. These cam elements 46 are interconnected by the shaft 50- which extends between the side plates 9 fixed to opposite sides of the circuit breaker frame 11. Each of the cams 46 may be fixed to shaft 50 by means of a cylindrical hub or hearing journal 51 welded to the cam 46 and pinned tothe shaft 5%. Hub 51 is supported and guided for transverse movement on the framework of the circuit breaker unit by a bearing means which comprises a pair of registering slots 53 formed in side plates 9 of the framework. Each cylindrical hub 51 fits freely into one of the slots 53 so that when the cam 46-is rotated, thev hub 51 may roll or slide with little friction within the slot so as to permit transverse movement of the axis 47 relative to the supporting circuit breaker unit 10, as will appear in greater detail hereinafter. Each cam element 46 is pro vided with a pair of curved or involute cam slots 54: and 55 which, respectively, are adapted to engage an anchor pin 56 fixed to the stationary cubicle unit 12 and areaction pin 57 fixed to the movable circuit breaker unit 1%) whereby to couple the units operatively together. These cam slots are eccentrically disposed with respect toaxis 47 so that pivotal movement of the cam element 46 about axis 47 will vary the distance between pins 56 am 57, thereby resulting in relative movement between the circuit breaker unit it} and the cubicle l2. Slot 55 is preferably formed as a closed end slot as shown since it is always engaged with pin 57 fixed on the breaker unit; but slot 54 has an open end-which permits disengagemerit therefrom of the cubicle anchor pin 56' whenever the cam is rotated into the pin-and-slot registering position shown in Fig. 3'.

From the above description of thecam means 45, it will be apparent that rotation of the transversely-movable cam element 46 while the fixed anchor pin 56 is properly engaged in slot 54 will not only shift the circuit breaker unit 10 in accordance with the configuration of cam slot 54 but will also shift the unit It) in accordance with the configuration of cam slot 55, the total amount of shifting depending upon the additive slope of the two cam slots 54 and 55 with respect to the shaft axis- 47. The cam. slots 54- and 55 are oppositely eccentrically disposed so that, for a given direction of rotation of cam 46,- the' pins- 56- and 57 both move. in radially opposite direct-ions with respect to the axis 47 of the cam element 46. Thus, it will be apparentthat a high degree of relative movement between pins 56 and 57, and accordingly, unit ltl and cubicle 12,- can be obtained from a comparatively small degree of rotation or stroke of the operating lever 48. As a result of the very small amount of pivotal motion required from operating lever 48, this invention makes it possible to dispense with the complex pawl and ratchet mechanisms conventionally used where small operating strokes are required. The exact operational characteristics of the cam mechanismwill become more apparent as the description proceeds.

in order to rotate cam element 46' by means of operating: lever 48, it is first necessary to withdraw the lever 48: from the position shown in Fig. 1 to the position of Fig. 2. The lever 48' has a pivot pin 60 fixed to one end and. is supported by thispivot pin 60, which is disposed in: a slot-61 provided in a bracket 63-mounted on the side plate 9 of the circuit breaker unit 10. A guide pin 62 is fixed to the: operating lever, and this guide pin 62, through its interference with an overhanging edge of the bracket 63, serves to prevent rotation of the lever 48 and; alsothe cam 46 when the lever is disposed in the retracted position of Fig. 1. Thus, to render the lever 48' operableto effect clockwise movement of. carn element 46 for disconnecting the unit from the cubicle, the lever 48- must first be withdrawn to the operative position of Fig. 2,. and in this position the guide pin 62 becomes freed from its blocking engagementwith the bracket 63. An upward: clockwise working stroke of the operating lever 48. about its pivot pin 60 may then be eflected. The axis of pivot pin 60 is captured in a fixed location at the left hand end. of the slot6 1 during this pivotal movement due to the guide pin 62 riding upon an arcuate edge 6321 provided on the overhanging portion of the bracket 63.

In. accordance with this invention, there is provided an interlockimeans 65 for tripping the breaker whenever the operating lever 48 is Withdrawn to the position in which itis capable of'producing movement of the circuit breaker unit 10. This interlock means- 65- comprises a trip plate- 66. which is operatively connected between the trip pin 19- and the lever 48 and isarranged to move into and out of apositio'n of interference with trip pin 19. This trip plate: 66: is pivotally mounted at 67 on the circuit breaker unit' and isadapted to be. rotated in a clockwise direction about point 67 by withdrawal of the lever 48 from the position of Fig. 1 to the position of Fig. 2. This clockwise motion of trip plate 66' causes the upper surface: 68 of the trip plate to engage the trip pin 19 and: move it upwardly to trip open the breaker, if closed; or if already open, preventingits closing due to the tripping latch. being rendered inoperative; in order to transmit. the Withdrawal motion of lever 48 tothe trip plate 66,. there is provided in trip plate 66 a curved slot 69 in which. the pin 4%- fixed to lever 48 is adapted to: travel. The slot 6% is shaped so as to have a center of curvature coincident'witlr the axis of pin 66. while the parts are inthe: position of Figs. 2' and 3, so that pivotal movement: of the lever 48 from the position of Fig. 2 tothe positionof Fig. 3 does not effectfurther rotation of trip plate 66 beyond the appropriate interlocking position produced. by the withdrawal of the lever from the position. of Fig. 1.

In addition to the above breaker unit trip plate 66 there is a second trip plate 70, which is pivotally mounted on a pivot 71 fixed to the stationary cubicle 12 through a bracket 72 secured to a side wall of the cubicle 12. This cubicle trip plate 70 is biased by a torsion spring 73 to rotate about pivot 71 in a counterclockwise direction so that it assumes the generally horizontal position of Figs. 2 and 3 except when the cubicle door 22 is closed, at which time it assumes the inclined position of Fig. 1 due to the engagement therewith of the door bracket 26. Thus, whenever the door 22 is opened the spring 73 is free to rotate the trip plate 79 into the position of Fig. 2, wherein the trip plate 71? is prevented from further rotation by the stop 74 projecting from the trip plate 70 and which is adatped to abut the upper surface of the bracket 72. In this pivoted position of Fig. 2 the upper cam surface 75 of the trip plate 79 is horizontally disposed in a plane extending immediately beneath the pin 19 in its tripped position. Thus, it will be apparent that as the circuit breaker unit is drawn out from the cubicle 12, as is described in greater detail hereinafter, the trip pin 19 will be moved to, or held in, its tripped position not only by the breaker trip plate 66 but also by the surface 75 of the cubicle trip plate 70. A valley 76 formed in the cubicle trip plate 70 removes the interference with pin 19 and so permits the closing of the circuit breaker for test purposes when the circuit breaker unit 10 is safely withdrawn from its connected position in the cubicle, as will also appear more clearly hereinafter.

Draw our operation In order to draw out the circuit breaker unit 10 from its connected position inside the enclosing cubicle 12 as shown in Fig. 1, the first requirement is to trip the circuit breaker 15 in case it is closed. Otherewise, as long as the circuit breaker 15 remains closed, the hook portion of the link 23 will engage the aperture 27 and lock the door 22 in the closed position thereby effectively preventing access of an operator to the drawout operating lever 48. By lifting the trip pin 19 from the position of Fig. l by a conventional linkage (not shown) manually operable from outside of the cubicle 12, tripping of the circuit breaker 15 may be effected. When the circuit breaker is so tripped, and the contact 16 has responded by separating from the fixed contact 17 to interrupt the circuit, the door 22 may then be opened so that the operating lever 48 becomes accessible to the operator. The operator then withdraws the lever 48 from the position of Fig. 1 to the operating position shown in Fig. 2, where the handle is then in a condition to effect rotation of the force amplifying cam mechanism 45. In the remote event that the circuit breaker had been closed again after the door 22 was opened but before the handle was withdrawn, in the preferred form of the invention, the circuit breaker would again be tripped by the breaker trip plate 66 of the interlock means 65 operated by withdrawal of the lever 48. Thus, with the circuit breaker in the position of Fig. 2, the circuit breaker unit 10 may be withdrawn from its connected position by pivoting of the lever 48 in a clockwise direction about pivot 60, thereby rotating the cam element 46 in a clockwise direction to the position of Fig. 3 where the pin 56 is adjacent the open end of slot 54. As previously explained, the small degree of rotation of cam element 46 from the position of Fig. 2 to the position of Fig. 3 will produce a Wide range of draw-out movement of the circuit breaker unit 10, due primarily to the double camming action provided by the cooperating cam slots 54 and 55. After the cam element has been rotated to the position of Fig. 3, the pin 56 is adjacent the open end of slot 54, the disconnect contacts 40 are disconnected, and thus, the circuit breaker unit 10 may be manually drawn further out on rollers 14 as desired. At least during the early part of the full drawing-out movement, the circuit breaker 15 will be maintained in tripped condition and prevented from closing because the trip pin 19 will be maintained at the vertical level of Fig. 2 by the upper surface 68 of the breaker unit trip plate 66 and also by the horizontal surface 75 of the cubicle trip plate 70. When the unit 10 has been withdrawn to that position in which the trip pin 19 is in vertical alignment with the valley '76 of the cubicle trip plate 70, there is a sufficiently safe distance between the separated disconnect contacts 40 and 41 to permit closing of the breaker without any hazard of establishing arcs between the disconnect contacts. This position is known as the test position, and here the circuit breaker may be opened and closed, as desired, for mechanical testing purposes. To close the breaker for testing, the lever 48 must first be lowered and retracted, as a result of which the breaker trip plate 66 will swing counterclockwise and the trip pin 19 will drop down into the valley 76, thereby permitting closing of the circuit breaker through the switch handle 18. From this test position, the circuit breaker unit 10 could be further withdrawn and, if desired, completely removed from cubicle 12.

Insert operation To insert the circuit breaker unit 10 into its connected position inside of the cubicle 12, the breaker on its carriage 13 is manually pushed on the rollers 14 toward the cubicle. After the breaker unit 10 has been moved past the test position, the upper surface 75 of the cubicle trip plate 70, through its engagement with trip pin 19, is effective to maintain the circuit breaker in the tripped open position. To move the circuit breaker unit into its connected position inside the cubicle, the operating handle 48 must first be withdrawn and raised to the position of Fig. 3. When the handle is so positioned, the unit 10 may be manually pushed into the cubicle until the open end of the cam slot 54 stops against the fixed pin 56, which is the position shown in Fig. 3. In this position, the trip pin 19 is held in tripped position by the upper surface of trip plate 66 and also by the upper surface 75 of trip plate 70, and thus, closing operation of the circuit breaker is effectively prevented. To move the unit 10 fully into the cubicle while forcing the disconnected contacts 40 into the circuit closing engagement with the circuit terminal contacts 41, the operating handle 48 now must be pushed downwardly in a counterclockwise direction about the pivot 60, thereby effecting rotation of cam element 46, which cooperates with pins 56 and 57 in the novel manner previously described to force the circuit breaker into the connected position of Fig. 2. At this point, the operating lever 48 may be retracted into the position of Fig. 1. This retracting movement of operating lever 48 permits the door 22 to be closed and also moves the pin 62 into blocking engagement with the lower surface of bracket 63. This blocking engagement prevents the cam element 46 from back tracking, or rotating in clockwise direction, thereby effectively locking the circuit breaker unit and the cubicle together in fully inserted position. Additionally, the retracting movement of lever 48 pivots the breaker trip plate 66 in a counterclockwise direction about pivot 67, whereby the trip pin is freed and the circuit breaker unit may be closed as desired.

As an alternative to the specific form of cubicle trip plate 70 shown, if desired, the cubicle trip plate 70 can be extended at its upper right hand end, as indicated by the dot-dash lines of Fig. 2, so as to be capable of engaging the trip pin 19 when the circuit breaker unit 10 is fully inserted, as shown in Fig. 2. Using such an alternative trip plate construction would prevent closing of the circuit breaker at all times during which the cubicle door 22 is opened, except, of course, when the circuit breaker unit is withdrawn to the test position.

Additionally, in accordance with the present invention, means other than the cam slot 55 and pin 57 may be employed for causing lateral displacement of the cam shaft 50 with respect to the circuit breaker unit 10. One

alternative is shown in Fig. 4, wherein a cam 46a, corresponding to the cam 46" previously described, has a cam slot 54a cooperating with a pin 56a fixed to the cubic and, additionally, has a hub 51a to which is secured a pinion 7'7. The hub is guided for movement with respect to the circuit breaker unit 10 by means of a slot 53a provided in the unit 11'). Fixed to the frame of the movable circuit breaker unit It) is a rack 78 which meshes with the pinion. When the cam is rotated about its axis, the rack and pinion are effective to' produce transverse shifting of the axis with respect to the circuit breaker unit 10. Thus, it will be seen that the rack and pinion produce a result similar to that produced by the cam 55 and pin 57 of Figs. 1-3.

While there has been shown and described particul'ar embodiments of the invention, it will be obvious to those skilled in the art that changes and modifications maybe made without departing from the invention, and that it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a movable circuit breaker unit, an enclosing unit receiving said circuit breaker unit, operating means for eifecting relative movement between said units and comprising an operating cam pivotable about an axis, said operating cam being supported on one of said units by guide means which permits movement of said. axis relative to said one unit, said operating cam having a pair of cam slots, 21' first element fixed to said enclosing unit, a second element fixed to said circuit breaker unit, each. of said elements being disposed to engage in one of said cam slots, said slots being oppositely eccentrically disposed with respect. to said axis so that when the elements and slots are engaged, pivoting of said operating cam about said axis will effect relative movement between said units in accordance with the configuration of both of said cam slots.

2. in combination, a movable unit, an enclosing unit receiving said movable unit, operating means for effecting relative movement between said units and comprising an operating cam pivotable about an axis, said operating cam being supported on one of said units by guide means which permits movement of said axis relative to said one unit, said operating cam having an opened-end cam slot eccentrically disposed with respect to said axis, an element fixed to the other of said units and disposed to engage in said cam slot so that pivotal movement of said cam will produce relative movement between said units, and means operative in response to pivotal motion of said cam for effecting movement of said axis relative to the unit on which said cam is supported.

3. In combination, a stationary unit and a movable circuit breaker unit associated therewith, cam means rotatable about an axis and disposed on one of said units, means for guiding the axis of said cam means in a predetermined path with respect to said one of said units, anchor structure disposed on the other of said units and cooperating with said cam means to adjustably couple said units together, and means operative in response to rotation of said cam means for causing movement of said axis along said guiding means.

4. in combination, an enclosing-cubicle andv a movable circuit breaker unit received therein, cam means rotatable about an axis and disposed on said circuit breaker unit, means for guiding the axis of said cam means in a predetermined path with respect to said circuit breaker unit, anchor structure disposed on the cubicle and cooperating with said cam means to adjustably couple together said cubicle and said circuit breaker unit, and means operative in response to rotation of said cam means for causing movement of said axis along said guiding means.

5. In combination, a movable circuit breaker unit and a cubicle unit for enclosing said movable unit, operating means for effecting relative movement between said units and comprising an opearting cam pivotable about an axis, said operating cam being supported on said circuit breaker unit by guide means which permits movement of said axis relative to said circuit breaker unit, said operating. cam having an opened-end cam slot eccentrically disposed with respect to said axis, an anchor element fixedly associated with said cubicle and disposed to engage in said cam slot so that pivotal movement of said cam will produce relative movement between said units, and means operative in response to pivotal motion of said cam for elfecting movement of said axis relative to said circuit breaker unit.

6. In combination, a stationary unit and a movable circuit breaker unit associated therewith, cam means rotatable about an axis and disposed on one of said units, means for guiding the axis of said cam means in a predetermined path with respect to said one of said units, anchor structure disposed on the other of said units and cooperating with said cam means to adjustably couple said. units together, and means comprising a rack and pinion operative in response to rotation of said cam means to cause movement of said axis along said guiding means.

7'. In combination, a stationary unit and a movable circuit breaker unit associated therewith, cam means rotatable about an. axis and disposed. on one of said units, means for guiding the axis of said cam means in a predetermined path with respect to said one of said units, anchor structure disposed on the other of said units and cooperating with said cam means to adjustably couple said units together, and means comprising a pin cooperating with a slot in said cam means operative in response to rotation of said cam means to cause movement of said axis along said guiding means.

8. In combination, a movable unit, an enclosing unit receiving said movable unit, operating means for effecting relative movement between said units and comprising an operating cam supported on one of said units for pivotal movement about an axis, said cam having a bearing journal, said cam-supportingunit having a guide bearing. for receiving and guiding said journal, said journal and bearingpermitting movement of said axis relative to said cam supporting unit, said operating. cam having a cam slot eccentrically disposed with respect to saidaxis, an element fixed to the other of said units and disposed to engage in said cam slot so that piovtal movement of said camwill produce relative movement of said units, and. means operative in response to pivotal movement of. said. cam for elfecting movement of said axis relative to the cam-supporting unit.

9. In combination, a movable circuit breaker unit comprising a circuit breaker having a trip element adapted to trip said circuit breaker, an enclosing unit receiving said circuit breaker unit, operating means for eflecting relative movement between said units and comprising an operating lever which has a retracted position and a withdrawn position, said operating lever being pivotable about a pivot mounted on one of said units to effect relative movement between said units, the pivot for said operating lever being shiftable between spaced apart positions on said one unit in response to movement of said lever between said retracted and withdrawn positions, means for locking. said operating lever against effective pivotal motion when in said retracted position and allowing eltective pivotal motion only when in said withdrawn position, interlock means operatively interconnecting said operating lever and said trip element, said interlock means being arranged to move said trip element to tripped position whenever said handle is moved to said withdrawn position.

10. In combination, a movable circuit breaker unit comprising a circuit brefler having a frame and a trip element adapted to trip said circuit breaker, an enclosing unit receiving said circuit breaker unit, operating means for elfecting relative movement between said units and comprising a cam and an operating lever which has a retracted position and a withdrawn position, said operating lever being pivotable about a pivot mounted on one of said units to effect relative movement between said units, the pivot for said operating lever being shiftable between said spaced-apart positions on said one unit in response to movement of said lever between said retracted and withdrawn positions, said operating lever having a projection cooperating with said frame to lock said lever and said cam against effective pivotal motion when the lever is in said retracted position, said lever being capable of effective pivotal motion only when in said withdrawn position, interlock means operatively interconnecting said operating lever and said trip element, said interlock means being arranged to move said trip element to tripped position whenever said handle is moved to said withdrawn position.

11. Switchgear apparatus comprising an enclosing unit, a circuit breaker unit movable into and out of said enclosing unit, operating means including a cam interconnecting said units and rotatable to efiect relative move- I0 ment between said units, an operating lever coupled to said cam and having a retracted and a withdrawn position, a pivot mounting said operating lever on one of said units and movable between spaced-apart positions on said one unit in response to movement of said operating lever between said retracted and withdrawn positions, said operating lever being pivotally movable when in said withdrawn position to effect rotation of said cam, and interference means rendered etfective by movement of said lever into said retracted position to lock said lever against pivotal movement and thus block rotation of said cam.

References Cited in the file of this patent UNITED STATES PATENTS 1,566,935 Trencham et al Dec. 22, 1925 1,632,592 French June 14, 1927 1,729,864 Brown Oct. 1, 1929 2,258,232 Atwood et al. Oct. 7, 1941 2,539,213 Von Mehren Jan. 23, 1951 2,540,814 Eichelberger Feb. 6, 1951 2,544,314 Hebbel Mar. 6, 1951 2,702,324 Donaldson Feb. 15, 1955 

